Two decades before police said Gary Martin, 45, opened fire at his co-workers, he was convicted of aggravated assault in Mississippi. Authorities there said he regularly abused a former girlfriend, at one point, hitting her with a baseball bat and stabbing her with a knife.

"All I can remember is him hitting and kicking me, I can remember fighting and screaming for help. I remember him pushing my head into that brick wall outside the apartment and thinking that he was going to kill me," the woman told police in Mississippi in 1994, according to court records.

The incident led to Martin's arrest. He pleaded guilty and was sentenced to five years in prison, though records show he served less than three years. He later moved to Aurora, Illinois, where he spent 15 years working at a warehouse, where he was able to buy a gun despite his felony record, and where, on Friday afternoon, violence erupted again.

Authorities in the Chicago suburb said Martin was called into a meeting at the Henry Pratt Co. warehouse. After he was told he was being fired, he began shooting, killing the three employees who were at the meeting and two others who were nearby, Aurora Police Chief Kristen Ziman told reporters Saturday. Among the dead was an intern on his first day at work.

Investigators have said little else that would explain the shooting spree, including why Martin was fired.

Police do not know if Martin knew of his termination and planned the shootout beforehand. But Dennis Rokop, a retired nuclear project manager, said that as a union employee, Martin was likely well aware that he was facing a termination meeting.

"You don't just fire a union guy," Rokop said. "You have to build a case against him. It's a big drawn-out process."

What police say they do know is that Martin showed up at the Henry Pratt Co. warehouse Friday armed with a Smith & Wesson handgun he was carrying illegally. Authorities also revealed Saturday that in January 2014, Martin was able to obtain an Illinois Firearm Owner's Identification Card despite his felony record, which Ziman said would not necessarily have shown up on a criminal background check conducted before he was issued the card. Some states and local jurisdictions provide incomplete records to the federal database, and sometimes human error leads to missed information.

The card is required to buy guns and ammunition in the state.

Martin also later bought a Smith & Wesson .40-caliber handgun and applied for a concealed carry permit, which required fingerprinting. During that process, officials discovered Martin's felony conviction. His application for a concealed carry permit was rejected and his FOID card was revoked. But there was no indication that authorities even confiscated his gun.

The shooting rampage has renewed criticisms that Illinois' laws allow many people to have access to guns even after their FOIDs have been revoked. In Illinois, those whose FOIDs have been revoked receive a notice from the Illinois State Police, telling them to surrender their card and list all the firearms in their possession. But the law does not explicitly require authorities to confiscate the firearms. Instead, the letter asks people to specify that they either no longer have possession of the firearms, or have given them to another person.

The shooting also carries echoes of the April 2018 shooting at a Waffle House in Tennessee involving a suspect who had obtained a FOID card from Illinois. Travis Reinking, who has been charged in that shooting, had previously been arrested for trying to cross a security barrier near the White House. As a result, Illinois authorities revoked his FOID card, took his guns and gave them to his father. But Reinking later got the weapons back.

"The fact remains is that some disgruntled person walked in and had access to a firearm that he shouldn't have had access to," Ziman told reporters, referring to Martin. "I don't want to make it political. This is a human issue. Lives were lost."

Wehner was killed on his first day as an intern at Henry Pratt. In a statement Saturday, Northern Illinois University president Lisa Freeman said Wehner was supposed to graduate in May with a degree in human resource management. Parks, an alumnus of the university, graduated in 2014.

A family friend of Wehner, Cynthia Rose Cascarano, described him in a Facebook post as a big brother to many boys in the community and a great role model.

"Each and every one of us have had a 'First Day' on the job," Cascarano wrote. "His should have never ended this way."

One warehouse employee suffered non-life-threatening gunshot wounds.

The five wounded officers are all expected to survive, police said. The officers, whose names were not released, are between ages 23 and 53. The youngest has been an officer for two years and the oldest for 30 years, authorities said. A sixth officer suffered a minor injury, though it was not caused by a gunshot.

Police were called to the scene just before 1:30 p.m. Friday. Within five minutes, Martin had shot the five officers who arrived at the 29,000-square-foot warehouse. He then hid in the warehouse, and police spent the next hour and a half finding him inside the massive facility. When police found Martin, he fired at the officers, who then killed him, Ziman said.

About 200 people work at Henry Pratt, which is owned by Atlanta-based Mueller Water Products. Scott Hall, the company's president and chief executive, told reporters Saturday that Martin was fired for "a culmination of a various workplace rules violations." Hall said Martin's felony record did not come up in a background check before the company hired him 15 years ago.

"Our hearts are with the victims and their loved ones, the first responders, the Aurora community and the entire Mueller family during this extremely difficult time," the company said in a statement.

Neil Van Milligan, a former supervisor who no longer works at Henry Pratt, said Martin worked for him sporadically over four years, usually packaging up valves.

"He had kind of an attitude," said Van Milligan, recalling how Martin repeatedly broke the rule against using cellphones on the plant floor.

"He'd just kind of look at you like you were stupid for telling him not to do something," Van Milligan said. "Knowing him and the way his attitude was, it doesn't surprise me that he got reprimanded."

Aside from his felony, Martin had been arrested six times by Aurora police on traffic and domestic violence issues. He was arrested most recently in 2017 by police in nearby Oswego, Illinois, for disorderly conduct and damage to property, authorities said.

Mississippi court records paint a picture of a disturbed man who frequently abused his former girlfriend, Chyreese Jones. Jones described Martin as a controlling man who "fakes" his remorse to seek attention. At one point, she told police, Martin held her and her 3-year-old daughter hostage inside their apartment, and threatened to kill her with a box cutter, court records say.

Jones, 52, brought charges against him after he stabbed her several times with a kitchen knife in Mississippi in March 1994.

"He doesn't take loss or rejection at all," Jones said. "He is going to be in charge. He is going to have something, a knife or a gun, and he is going to win."

On March 8, 1994, Jones asked Martin, then 20, to pack his belongings at her apartment because she wanted to end the relationship. Martin told Jones that if they were going to end their relationship, they were "going to go out with a bang," she told police at that time.

"'We are all going to die'" Jones told police Martin said. "That's when (he) began to hit me."

He kicked her in the stomach and hit her with the baseball bat, court records say. Jones ran to her neighbors, and police later found her bleeding from several stab wounds, including two deep cuts to her neck.

While in prison, Martin wrote to Jones. In one letter, he appeared to blame others for his problems, telling Jones that "they" were doing everything to keep him incarcerated.

"I don't know how much longer I can keep my thoughts to myself. I've got so much to say but I don't know who to say them to ... This pain and hurt is with me day and night and I just can't seem to shake it," Martin wrote.

At the end of the letter, he said, "Give Vozzie a big hug and kiss for me," referring to Jones' daughter.

On Saturday, neighbors in the cluster of three-story apartment buildings where Martin lived, in a blue-collar neighborhood on the outskirts of Aurora, said some had heard Martin was fighting to keep his job.

Steve Spizewski, who lived three doors down from Martin, saw another, kinder side to him. They would hang out together, Spizewski said, playing video games or watching movies.

When Spizewski's mother passed away recently, Martin was the person who consoled him. Spizewski's never thought of Martin as a man who might use a weapon.

"I knew he had an air rifle," he said. "I didn't know he had a 'gun' gun."

But Spizewski also said Martin had a troubled recent relationship with a girlfriend who had damaged his car and had mounted a camera on a post overlooking his assigned parking spot to protect his prized possession.

When Spizewski last saw Martin earlier this week, though, he had no idea that anything was wrong.

"He had a cigar in his mouth, a fedora on his head," Spizewski said.

Martin often bought cigars from a Circle K not far from where he lived, where he struck up a friendship with Ricardo Moreno, an assistant manager.

Martin came in almost every morning as he left for work on the early shift, and would purchase two to three cigars - the "Black and Mild Jazz" brand.

The two men bonded over 30-minute conversations that ranged from talking about women to the news. When mass shootings, notably Las Vegas and Parkland, were in the headlines, Martin didn't have much to say.

"He tried to stay away from bad vibes," Moreno said.

He also never talked about partying or going to the bars, said Moreno, noting he mostly stayed at home.

Moreno said he last talked with Martin two weeks ago, when he said he was dating a new woman.

"Life's good, everything's going good," he said Martin told him.

Jones attributed Martin's anger to problems that dated to his childhood in Aurora. He never had a father-figure in his life, she said, and he had such a strained relationship with his mother that he moved to Mississippi where he lived with his grandmother and other relatives.

"He is a nice guy - was a nice guy," she said, "But he was dealing with demons of some sort and he couldn't chase."

Martin's mother declined to comment.

The shooting in Aurora occurred just a day after the first anniversary of a mass shooting that killed 17 students and staffers at Marjory Stoneman Douglas High School in Parkland, Florida. The young survivors have since become among the loudest advocates for stronger gun laws, spurring a social media movement with the hashtag #NeverAgain. Their activism has led to the creation of the student-led demonstration, March for our Lives.

Aurora shares a name with a Denver suburb that endured a mass shooting almost seven years ago. A gunman, James Holmes, opened fire inside a movie theater in 2012, killing 12 people and injuring 70 others. The similarity was not lost on Nick Metz, the police chief of Aurora, Colo.

"Months from now as people talk about the mass shooting in Aurora, someone will ask, 'Which Aurora mass shooting are we talking about?'" he said on Twitter.